Brinell Hardness Testers



There exist three main stationary methods of hardness measurements. These are Rockwell, Brinell and Vickers tests. Brinell method is named after Swedish engineer J.Brinell. It is based on the penetration of a steel or hard-alloy ball indenter into the tested material under load and consequent measurement of the mean diameter of the restored indentation. Usually two diameters of the indentation are measured in mutually perpendicular directions and then the mean value of the indentation diameter is calculated. The indentation diameter should be greater than the ball diameter multiplied by 0,24 and less than the ball diameter multiplied by 0,6.

Brinell hardness testers implement this method directly, i.e. a steel or hard-alloy ball of a known diameter and with a known load penetrates perpendicularly into the tested sample. After that a restored diameter of the indentation is measured with the help of an optical system and Brinell hardness is measured using known values of the load, as well as ball and indentation diameters. Most frequently Brinell hardness testers use balls with diameters of 1 mm; 2,5 mm, 5 mm, 10 mm. Most common loads for Brinell hardness testers are as follows: 10 kgf; 30 kgf; 62,5 kgf; 187,5 kgf; 250 kgf; 750 kgf; 1000 kgf; 3000 kgf, but other loads might be used as well. The value of the load and ball diameter in Brinell hardness testers is chosen on the grounds of satisfying the stated above correlations for the value of restored indentation diameter. During measurements on steel samples the holding time under load is set in between 10 and 15 seconds. The softer the tested sample, the longer the load in Brinell hardness tester should be applied. According to Russian standards, the error limits of Brinell hardness testers on test blocks of 100 HB, 200 HB, 400 HB equal 3 %. The main influence on Brinell hardness testers accuracy is made by the following key parts: load application device, optical system, indenter. If Brinell hardness testers have a compound lever system of load application, the influence on the hardness error will be higher than that of the load application systems with stepper motor or direct load. The optical system of Brinell hardness testers is intended for measurements of the restored indentation diameter. Most frequently this system consists of a microscope inbuilt into the hardness tester. Its magnification and resolution should make it possible to measure the indentation diameter accurately.

Brinell hardness testers are used for hardness measurements on soft and medium samples with quite roughly finished or heterogeneous surface.


See also:

Miniature ultrasonic hardness testers

Rockwell hardness tester -HRC
-HRC / MET-RC50
Rockwell
hardness tester
Brinell hardness tester -HB
-HB / MET-B50
Brinell
hardness tester
Vickers hardness tester
-HV / MET-V50
Vickers
hardness tester
Shore hardness tester MET-HSD
MET-HSD / MET-HSD50
Shore
hardness tester


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